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CN119403760A - Silicon dioxide particles and method for producing the same, silica sol, polishing composition, polishing method, method for producing semiconductor wafer, and method for producing semiconductor device - Google Patents

Silicon dioxide particles and method for producing the same, silica sol, polishing composition, polishing method, method for producing semiconductor wafer, and method for producing semiconductor device Download PDF

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Publication number
CN119403760A
CN119403760A CN202380048239.3A CN202380048239A CN119403760A CN 119403760 A CN119403760 A CN 119403760A CN 202380048239 A CN202380048239 A CN 202380048239A CN 119403760 A CN119403760 A CN 119403760A
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silica particles
polishing
silica
less
mass
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岛田裕太
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Mitsubishi Chemical Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
    • C01B33/145—Preparation of hydroorganosols, organosols or dispersions in an organic medium
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09G—POLISHING COMPOSITIONS; SKI WAXES
    • C09G1/00—Polishing compositions
    • C09G1/02—Polishing compositions containing abrasives or grinding agents
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K3/00—Materials not provided for elsewhere
    • C09K3/14—Anti-slip materials; Abrasives
    • C09K3/1409—Abrasive particles per se
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/304—Mechanical treatment, e.g. grinding, polishing, cutting
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/14—Pore volume
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/16—Pore diameter
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/60—Optical properties, e.g. expressed in CIELAB-values
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/80—Compositional purity
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
    • H01L21/30625—With simultaneous mechanical treatment, e.g. mechanico-chemical polishing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
    • H01L21/3105—After-treatment
    • H01L21/31051—Planarisation of the insulating layers
    • H01L21/31053—Planarisation of the insulating layers involving a dielectric removal step
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
    • H01L21/3205—Deposition of non-insulating-, e.g. conductive- or resistive-, layers on insulating layers; After-treatment of these layers
    • H01L21/321—After treatment
    • H01L21/32115—Planarisation
    • H01L21/3212—Planarisation by chemical mechanical polishing [CMP]

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Inorganic Chemistry (AREA)
  • Dispersion Chemistry (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • General Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Manufacturing & Machinery (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Silicon Compounds (AREA)
  • Mechanical Treatment Of Semiconductor (AREA)
  • Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)

Abstract

本发明的目的在于，提供机械强度、研磨特性以及保存稳定性优异的二氧化硅粒子、硅溶胶、研磨组合物。本发明涉及一种二氧化硅粒子，其中，通过正电子湮没法测定出的原子级细孔的平均孔容为0.35nm3以上。The present invention aims to provide silica particles, silica sol and abrasive compositions having excellent mechanical strength, polishing properties and storage stability. The present invention relates to silica particles having an average pore volume of atomic-scale pores of 0.35 nm 3 or more as measured by positron annihilation.

Description

Silica particles and method for producing same, silica sol, polishing composition, polishing method, method for producing semiconductor wafer, and method for producing semiconductor device
Technical Field
The present invention relates to silica particles and a method for producing the same, silica sol, polishing composition, polishing method, method for producing semiconductor wafer, and method for producing semiconductor device.
Background
As a method for polishing the surface of a material such as a metal or an inorganic compound, a polishing method using a polishing liquid is known. Among them, in Chemical Mechanical Polishing (CMP) of an original (prime) silicon wafer for a semiconductor, final finish polishing of a regenerated silicon wafer thereof, planarization of an interlayer insulating film at the time of manufacturing a semiconductor device, formation of a metal plug (plug), formation of a buried wiring, and the like, the surface state thereof has a great influence on semiconductor characteristics, and therefore, it is required that the surfaces and end faces of these components be polished with extremely high precision.
In such precision polishing, a polishing composition containing silica particles is used, and colloidal silica is widely used as abrasive grains as a main component thereof. Colloidal silica is known, depending on the production method thereof, from colloidal silica (fumed silica or the like) obtained by thermal decomposition of silicon tetrachloride, colloidal silica obtained by deionization of alkali metal silicate such as water glass, colloidal silica obtained by hydrolysis reaction and condensation reaction of alkoxysilane (generally referred to as "sol-gel method"), and the like.
As for the method for producing silica particles, many studies have been made so far. For example, patent documents 1 to 2 disclose a method for producing silica particles by hydrolysis reaction and condensation reaction of alkoxysilane.
Prior art literature
Patent literature
Patent document 1 Japanese patent laid-open No. 11-60232
Patent document 2 Japanese patent application laid-open No. 2019-89692
Disclosure of Invention
Problems to be solved by the invention
In general, silica particles obtained by hydrolysis reaction and condensation reaction of alkoxysilane are not necessarily said to be chemically or physically stable. More specifically, the mechanical strength of such conventional silica particles and the storage stability of such conventional silica particles due to environmental factors as irradiation with ultraviolet rays and an increase or decrease in temperature are not necessarily sufficient. Further, when silica particles having insufficient mechanical strength and storage stability are used for polishing, the silica particles are broken by physical impact during polishing, and the broken silica particles adhere to a polishing object or the like, thereby adversely affecting polishing.
The silica particles obtained by the production methods disclosed in patent documents 1 to 2 are inferior in mechanical strength, polishing characteristics and storage stability.
The present invention has been made in view of the above problems, and an object of the present invention is to provide silica particles, silica sol, and polishing composition which are excellent in mechanical strength, polishing characteristics, and storage stability. Another object of the present invention is to provide a polishing method, a semiconductor wafer manufacturing method, and a semiconductor device manufacturing method, each of which has excellent productivity of a workpiece to be polished.
Means for solving the problems
The mechanical strength, polishing characteristics and storage stability of conventional silica particles are not necessarily sufficient. The present inventors have paid attention to deformation of a siloxane network of silica particles, which is a cause of deterioration in mechanical strength, polishing characteristics, and storage stability of the silica particles, and have conducted intensive studies to reduce the deformation of the siloxane network of the silica particles. As a result, the inventors have found that the deformation of the siloxane network of the silica particles is closely related to the size of the fine pores of the silica particles. Further, the present inventors have found that by optimizing the average pore volume of atomic scale micropores measured by positron annihilation, deformation of the siloxane network of silica particles can be reduced, and mechanical strength, polishing characteristics, and storage stability of silica particles can be improved, thereby completing the present invention.
Namely, the gist of the present invention is as follows.
[1]
A silica particle having an average pore volume of atomic-scale micropores measured by positron annihilation of 0.35nm 3 or more.
[2]
The silica particle according to [1], wherein the average pore volume of the atomic-scale micropores measured by positron annihilation is 0.40nm 3 or more.
[3]
The silica particle according to [1], wherein the average pore volume of the atomic-scale micropores measured by positron annihilation is 1.0nm 3 or less.
[4]
The silica particle according to [1], wherein the average pore volume of the atomic-scale micropores measured by positron annihilation is 0.80nm 3 or less.
[5]
The silica particle according to [1], wherein the average pore volume of the nano-scale pores measured by positron annihilation is 5.4nm 3 or less.
[6]
The silica particles according to [1], wherein the volume of pores having a diameter of 2nm or less as measured by the nitrogen adsorption method is 0.0070cm 3/g or less.
[7]
The silica particles according to [1], wherein the refractive index is 1.390 or more.
[8]
The silica particles according to [1], wherein the metal impurity content is 5ppm or less.
[9]
The silica particles according to [1], wherein the silica particles comprise a tetraalkoxysilane condensate as a main component.
[10]
A method for producing silica particles according to any one of [1] to [9], comprising a step of carrying out hydrolysis reaction and condensation reaction of alkoxysilane in 600 minutes or less.
[11]
A silica sol comprising the silica particles according to any one of [1] to [9 ].
[12]
A polishing composition comprising the silica sol according to [11 ].
[13]
A polishing method by using the polishing composition according to [12 ].
[14]
A method for producing a semiconductor wafer, comprising the step of polishing with the polishing composition according to [12 ].
[15]
A method for producing a semiconductor device, comprising the step of polishing with the polishing composition according to [12 ].
Effects of the invention
The silica particles of the present invention have improved mechanical strength, polishing characteristics and storage stability. In the step of polishing the object to be polished using the polishing composition containing the silica particles, the silica particles of the present invention are less likely to be damaged.
Therefore, the silica sol and the polishing composition containing the silica particles of the present invention can be used to effectively polish an object to be polished without damaging the object to be polished, and the silica particles after polishing can be easily removed. Therefore, a high-quality abrasive article can be produced with good productivity.
Detailed Description
The present invention will be described in detail below, but the present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist thereof. In the case where the expression "-" is used in the present specification, the expression "is used as an expression including numerical values before and after the expression" and physical properties ".
(Silica particles)
The average pore volume of the atomic scale micropores (hereinafter also simply referred to as "average pore volume of atomic scale micropores") of the silica particles of the present invention measured by positron annihilation method is 0.35nm 3 or more, preferably 0.40nm 3 or more, and more preferably 0.42nm 3 or more. This reduces deformation of the siloxane network of the silica particles, and improves the mechanical strength, polishing characteristics, and storage stability of the silica particles.
The reason why the siloxane network of the silica particles is deformed is considered to be that the growth rate of the silica particles is too slow, and therefore, a plurality of four bonding bonds of the silicon atoms form bonds with bonding bonds of the adjacent silicon atoms, and a more stable structure cannot be formed. The deformation of the siloxane network affects the size of the atomic scale pores. This is because, if the bonding bond between the silicon atom and the adjacent silicon atom forms a bond, the space within the ring surrounded by the siloxane structure becomes smaller. The deformed siloxane network structure becomes a cause of the decrease in mechanical strength of the silica particles. Further, the deformed silica particles having a siloxane network structure have poor storage stability because chemical bonds are easily broken due to environmental factors such as irradiation of ultraviolet rays and an increase or decrease in temperature. When the deformed silica particles having a siloxane network structure are used for polishing, the silica particles are broken by physical impact during polishing, and the broken silica particles adhere to a polishing object or the like, thereby adversely affecting polishing.
It is considered that, when the average pore volume of the atomic scale micropores is set to the above range, the deformation of the siloxane network is effectively reduced, and the mechanical strength, polishing characteristics and storage stability of the silica particles are improved.
The upper limit of the average pore volume of the atomic-scale micropores of the silica particles is not particularly limited, but is preferably 1.0nm 3 or less, more preferably 0.80nm 3 or less, and still more preferably 0.60nm 3 or less, in order to maintain mechanical strength.
Positron annihilation is a method of measuring the lifetime of positrons by a time difference between the moment when a positron is emitted and the moment when a gamma ray generated when positron annihilation is observed. The material has a property that the lifetime of positrons is longer as the number of vacancy defects in the material is larger when positrons are injected into the material. By utilizing this property, the average pore volume of the atomic-scale pores and the average pore volume of the nano-scale pores described later can be measured.
The average pore volume of the atomic-scale micropores of the silica particles in the present specification means a value measured by positron annihilation. Specifically, the positron lifetime spectrum obtained by applying the positron annihilation method to the dried silica particles is fitted to the linear sum of four exponential functions, and the average lifetime of the positrons of each component is obtained. Of these four exponential function components, two components with short lives are components independent of materials. The third component having the shortest lifetime is a component corresponding to an atomic-scale pore, and the average lifetime is substituted into the following equation and converted into the volume of the pore, thereby obtaining the average pore volume. The average pore volume of the atomic-scale pores of the obtained silica particles can be grasped as the volume of the pores in the ring structure of the siloxane network, and the volume of the pores is mainly 1nm 3 or less in the silica particles.
The relationship between positron lifetime and pore volume is referred to by the formula K.Wada et al, J.Phys.: conf.Ser.443, 01003 (2013).
[ Number 1]
Wherein,
[ Number 2]
Τ is the average lifetime of positrons, R is the average radius of atomic scale pores, Δr is a correction value for the radius of atomic scale pores, and V is the average pore volume of atomic scale pores.
The component having the longest lifetime is a component corresponding to a nano-pore described later.
As a method for measuring the pore volume, there are other methods using gas adsorption and desorption such as a nitrogen adsorption method, but there is a problem in that the gas adsorption and desorption method cannot measure closed pores and errors occur in measurement results due to chemical interactions between a measurement object and a probe gas. The positron annihilation method also enables measurement of the volume of the closed hole, and thus enables highly accurate measurement, regardless of the surface state of the object to be measured.
From the viewpoint of further improving the mechanical strength, polishing characteristics and storage stability of the silica particles, the average pore volume of the nano-sized pores (hereinafter also simply referred to as "average pore volume of the nano-sized pores") of the silica particles measured by the positron annihilation method is preferably 5.4nm 3 or less, more preferably 5.3nm 3 or less, and still more preferably 5.2nm 3 or less. In order to maintain the flexibility of the particles and prevent the particles from being damaged during polishing, the average pore volume of the nano-sized pores is preferably 1.5nm 3 or more, more preferably 2.5nm 3 or more, and even more preferably 3.5nm 3 or more.
The average pore volume of the nano-scale pores of the silica particles in the present specification is a value measured by positron annihilation. Positron lifetime spectra were obtained by the same method as the measurement of the average pore volume of atomic scale pores, fitting was performed with four components, and the average lifetime of the component having the longest lifetime was substituted into the following formula, converted into the pore volume, and the average pore volume of the nano scale pores was obtained. From the average pore volume of the nano-sized pores of the obtained silica particles, the volume of pores having a volume of more than 1nm 3 in the silica particles, such as pores surrounded by si—o-Si structure, silanol group and/or alkoxy group, can be grasped.
[ Number 3]
Wherein,
[ Number 4]
Τ is the average lifetime of positrons, R is the average radius of the nano-sized pores, R 0 is the correction value of the radius of the nano-sized pores, λ T is the annihilation rate of normal electron-even in vacuum, and V is the average pore volume of the nano-sized pores.
The mechanical strength of the silica particles can be adjusted by Kong Ronglai. From this viewpoint, the volume of the pores having a diameter of 2nm or less as measured by the nitrogen adsorption method is preferably 0.0070cm 3/g or less, more preferably 0.0060cm 3/g or less, and still more preferably 0.0050cm 3/g or less. Further, from the viewpoint of maintaining the flexibility of the structure of the silica particles, the volume of the micropores having a diameter of 2nm or less as measured by the nitrogen adsorption method is preferably 0.0005cm 3/g or more, more preferably 0.0010cm 3/g or more, and still more preferably 0.0015cm 3/g or more.
When the refractive index of the silica particles is large, the atomic density of the silica particles is high, and the mechanical strength is easily maintained, so that the refractive index is preferably 1.390 or more, more preferably 1.400 or more, and further preferably 1.410 or more. Further, since the silica preferably maintains an amorphous structure, the refractive index is preferably 1.550 or less, more preferably 1.500 or less, and further preferably 1.450 or less.
The refractive index of the silica particles was measured with an Abbe refractometer on the supernatant liquid when the silica particles in the container became transparent by adding the mixture of superfine 2-propanol and superfine toluene to the container in which the silica particles were contained, and the refractive index at this time was taken as the refractive index of the silica particles.
The silica particles are preferably amorphous. In this case, silanol groups are moderately present on the surface of the silica particles, and in the step of polishing the object to be polished, chemical action is generated between the silica particles and the object to be polished via the silanol groups, and polishing proceeds satisfactorily.
The amorphous state of the silica particles can be confirmed by a halo pattern in wide-angle X-ray scattering measurement.
The metal impurity content of the silica particles is preferably 5ppm or less, more preferably 2ppm or less.
When the metal impurity content of the silica particles is 5ppm or less, contamination due to adhesion of metal impurities to the surface of the object to be polished is reduced in polishing a silicon wafer of a semiconductor device, and thus the influence on the wafer characteristics is reduced, which is preferable. Further, it is preferable that degradation of quality due to diffusion of metal impurities adhering to the surface of the object to be polished into the wafer is reduced, and degradation of performance of semiconductor devices manufactured from such wafers is reduced.
Further, when the metal impurity content of the silica particles is 5ppm or less, it is preferable that the influence of the change in chemical properties (acidity or the like) of the surface silanol groups and the change in the three-dimensional environment (easiness of aggregation of the silica particles or the like) of the silica particles on the polishing rate is reduced, which is caused by the occurrence of the coordination interaction between the surface silanol groups which exhibit acidity and the metal impurities.
The metal impurity content of the silica particles in the present specification means a value measured by high-frequency inductively coupled plasma mass spectrometry (ICP-MS). Specifically, a silica sol containing 0.4g of silica particles was accurately measured, sulfuric acid and hydrofluoric acid were added, heated, dissolved, evaporated, and pure water was added to the residual sulfuric acid droplets so that the total amount became 10g, to prepare a test solution, and the test solution was measured by a high-frequency inductively coupled plasma mass spectrometry device. The metals to be treated are sodium, potassium, iron, aluminum, calcium, magnesium, zinc, cobalt, chromium, copper, manganese, lead, titanium, silver, and nickel, and the total content of these metals is defined as the metal impurity content.
The metal impurity content of the silica particles can be set to 5ppm or less by subjecting alkoxysilane as a main raw material to hydrolysis reaction and condensation reaction to obtain silica particles.
In the method of deionizing an alkali metal silicate such as water glass, since sodium or the like derived from the raw material remains, it is extremely difficult to set the metal impurity content of silica particles to 5ppm or less.
The average primary particle diameter of the silica particles is preferably 10nm to 100nm, more preferably 15nm to 60nm, and even more preferably 30nm to 50nm. When the average primary particle diameter of the silica particles is 10nm or more, the storage stability of the silica sol is excellent. Further, when the average primary particle diameter of the silica particles is 100nm or less, surface roughness and damage of the object to be polished represented by the silicon wafer can be reduced, and sedimentation of the silica particles can be suppressed.
The average primary particle diameter of the silica particles was measured by the BET method. Specifically, the specific surface area of the silica particles was measured using an automatic specific surface area measuring device, and the average primary particle diameter was calculated using the following formula (2).
Average primary particle diameter (nm) =6000/(specific surface area (m 2/g) ×density (g/cm 3))..
The average primary particle diameter of the silica particles may be set to a desired range depending on the conditions for producing the silica particles.
The average secondary particle diameter of the silica particles is preferably 20nm to 200nm, more preferably 30nm to 100nm, and even more preferably 55nm to 80nm. When the average secondary particle diameter of the silica particles is 20nm or more, the removability of particles or the like at the time of cleaning after polishing is excellent, and the storage stability of the silica sol is excellent. Further, when the average secondary particle diameter of the silica particles is 200nm or less, surface roughness and damage of the object to be polished represented by the silicon wafer during polishing can be reduced, and the removal performance of particles and the like during cleaning after polishing is excellent, and sedimentation of the silica particles can be suppressed.
The average secondary particle diameter of the silica particles was measured by the DLS (DYNAMIC LIGHT SCATTERING: dynamic light scattering) method. Specifically, the measurement was performed using a dynamic light scattering particle size measurement device.
The average secondary particle diameter of the silica particles may be set to a desired range depending on the conditions for producing the silica particles.
The cv (coefficient of variation: coefficient of variation) value of the silica particles is preferably 10% to 50%, more preferably 15% to 40%, still more preferably 20% to 35%. When the cv value of the silica particles is 10% or more, the polishing rate to the object to be polished represented by a silicon wafer is excellent, and the productivity of the silicon wafer is excellent. Further, when the cv value of the silica particles is 50% or less, surface roughness and damage of the object to be polished represented by the silicon wafer during polishing can be reduced, and the removal property of particles and the like during cleaning after polishing is excellent.
The cv value of the silica particles was measured by a dynamic light scattering particle diameter measuring device, and the average secondary particle diameter of the silica particles was calculated by the following formula (3).
Cv value = (standard deviation (nm)/average two secondary particle size (nm)) x 100..the term (3)
The association ratio of the silica particles is preferably 1.0 to 4.0, more preferably 1.1 to 3.0. When the association ratio of the silica particles is 1.0 or more, the polishing rate to the object to be polished represented by a silicon wafer is excellent, and the productivity of the silicon wafer is excellent. When the association ratio of the silica particles is 4.0 or less, the surface roughness and damage of the object to be polished, typically a silicon wafer, during polishing can be reduced, and aggregation of the silica particles can be suppressed.
The association ratio of the silica particles is calculated from the average primary particle diameter measured by the measurement method and the average secondary particle diameter measured by the measurement method using the following formula (4).
Association ratio = average secondary particle diameter/average primary particle diameter..4.. (4)
The silica particles of the present invention preferably contain an alkoxysilane condensate as a main component, more preferably a tetraalkoxysilane condensate as a main component, and even more preferably a tetramethoxysilane condensate as a main component, because the content of metal impurities is small and the mechanical strength and storage stability are excellent. The main component is a component of 50 mass% or more of 100 mass% of the total components constituting the silica particles.
In order to obtain silica particles containing an alkoxysilane condensate as a main component, an alkoxysilane is preferably used as a main raw material. In order to obtain silica particles containing a tetraalkoxysilane condensate as a main component, a tetraalkoxysilane is preferably used as a main raw material. In order to obtain silica particles mainly composed of a tetramethoxysilane condensate, tetramethoxysilane is preferably used as a main raw material. The main raw material is a raw material of 50 mass% or more of 100 mass% of the total raw materials constituting the silica particles.
The surface silanol group density of the silica particles of the present invention is preferably 1/nm 2 to 8/nm 2, more preferably 4/nm 2 to 7/nm 2. When the surface silanol group density of the silica particles is 1/nm 2 or more, the silica particles have moderate surface repulsion and the dispersion stability of the silica sol is excellent. In addition, when the surface silanol group density of the silica particles is 8/nm 2 or less, the silica particles have moderate surface repulsion, and aggregation of the silica particles can be suppressed.
The surface silanol group density of the silica particles was measured by the sierss method. Specifically, measurement and calculation were performed under the following conditions.
Silica sol corresponding to 1.5g of silica particles was collected, and pure water was added so that the liquid amount became 90mL. In an environment of 25 ℃, 0.1mol/L aqueous hydrochloric acid solution was added until the pH became 3.6, 30g of sodium chloride was added, and while slowly adding pure water, sodium chloride was completely dissolved, and pure water was added until the total amount of the final test solution became 150mL, to obtain a test solution.
The obtained test solution was placed in an automatic titration apparatus, and 0.1mol/L aqueous sodium hydroxide solution was added dropwise thereto to measure the titration amount A (mL) of the 0.1mol/L aqueous sodium hydroxide solution required for the pH to change from 4.0 to 9.0.
The consumption amount V (mL) of the aqueous sodium hydroxide solution of 0.1mol/L required for changing the pH of the silica particles from 4.0 to 9.0 was calculated for each 1.5g of the silica particles using the following formula (5), and the surface silanol group density ρ (number/nm 2) of the silica particles was calculated using the following formula (6).
V=(A×f×100×1.5)/(W×C)......(5)
A titration amount (mL) of 0.1mol/L aqueous sodium hydroxide solution required for changing the pH of the silica particles from 4.0 to 9.0 per 1.5 g.
F titer of the aqueous sodium hydroxide solution used at 0.1 mol/L.
Concentration of silica particles in silica sol (mass%).
W is the collecting amount (g) of the silica sol.
ρ=(B×NA)/(1018×M×SBET)......(6)
The amount of sodium hydroxide (mol) required to change the pH per 1.5g of silica particles calculated from V from 4.0 to 9.0.
NA, avofila constant (units/mol).
M silica particle amount (1.5 g).
SBET the specific surface area (m 2/g) of the silica particles measured when the average primary particle diameter is calculated.
(Method for producing silica particles)
The silica particles of the present invention can be obtained by a process comprising hydrolysis reaction and condensation reaction of tetraalkoxysilane at pH8 to 14. In view of the easiness of controlling the hydrolysis reaction and the condensation reaction, the reaction rate of the hydrolysis reaction and the condensation reaction can be increased, gelation of the dispersion of silica particles can be prevented, and silica particles having uniform particle diameters can be obtained, it is preferable that the solution (A) containing water is added with the solution (B) containing tetraalkoxysilane and the solution (C) added as needed, and the tetraalkoxysilane is subjected to the hydrolysis reaction and the condensation reaction. The average pore volume of the atomic scale micropores and the average pore volume of the nano scale micropores of the silica particles can be set to the desired ranges by the conditions for producing silica particles such as pH, reaction temperature, reaction time, catalyst concentration, raw material supply rate, and the conditions for pressure heating treatment such as pressure, heating temperature, and pressure heating time. For example, the average Kong Rongyue of the atomic-scale micropores of the silica particles tends to be large as the reaction time of the hydrolysis and condensation reaction of the tetraalkoxysilane is shortened and the temperature and pressure of the pressure-heating treatment are increased. On the other hand, for example, the average Kong Rongyue of the nano-sized pores of the silica particles tends to be smaller as the reaction temperature of the hydrolysis and condensation reaction of the tetraalkoxysilane is higher and the reaction time of the hydrolysis and condensation reaction of the tetraalkoxysilane is longer.
The solution (a) contains water.
From the viewpoint of excellent dispersibility of the tetraalkoxysilane in the reaction solution, the solution (a) preferably contains a solvent other than water.
Examples of the solvent other than water in the solution (A) include methanol, ethanol, propanol, isopropanol, and ethylene glycol. These solvents may be used singly or in combination of two or more. Among these solvents, from the viewpoint of ease of dissolution of the tetraalkoxysilane, the solvents used in the hydrolysis reaction and the condensation reaction are the same as the by-product solvents, and from the viewpoint of excellent convenience in production, alcohols are preferable, methanol and ethanol are more preferable, and methanol is further preferable.
From the viewpoint of improving the reaction rate of the hydrolysis reaction and the condensation reaction of the tetraalkoxysilane, the solution (a) preferably contains a base catalyst.
Examples of the base catalyst in the solution (A) include ethylenediamine, diethylenetriamine, triethylenetetramine, ammonia, urea, ethanolamine, and tetramethylammonium hydroxide. These base catalysts may be used singly or in combination of two or more. Among these base catalysts, ammonia is preferred because of its excellent catalytic activity, easy control of particle shape, suppression of mixing of metal impurities, high volatility, and excellent removability after hydrolysis and condensation reactions.
The concentration of water in the solution (a) is preferably 3 to 90 mass%, more preferably 5 to 50 mass%, of 100 mass% of the solution (a). When the concentration of water in the solution (a) is 3 mass% or more, the hydrolysis reaction rate of the tetraalkoxysilane is easily controlled. When the concentration of water in the solution (a) is 90 mass% or less, the reaction balance between the hydrolysis reaction and the condensation reaction is good, and the particle shape can be easily controlled.
The concentration of the base catalyst in the solution (a) is preferably 0.5 to 2.0 mass%, more preferably 0.6 to 1.5 mass%, based on 100 mass% of the solution (a). When the concentration of the base catalyst in the solution (a) is 0.5 mass% or more, aggregation of silica particles is suppressed, and the dispersion stability of silica particles in the dispersion is excellent. When the concentration of the base catalyst in the solution (a) is 2.0 mass% or less, the reaction does not proceed too rapidly, and the reaction controllability is excellent.
The concentration of the solvent other than water in the solution (a) is preferably water and the remainder of the base catalyst.
Solution (B) contains a tetraalkoxysilane.
Examples of the tetraalkoxysilane in the solution (B) include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetraisopropoxysilane. These tetraalkoxysilanes may be used singly or in combination of two or more. Among these tetraalkoxysilanes, tetramethoxysilane and tetraethoxysilane are preferable, and tetramethoxysilane is more preferable, because hydrolysis reaction is fast, unreacted materials are not easily left, productivity is excellent, and stable silica sol can be easily obtained.
The silica particles may be produced from a material other than a tetraalkoxysilane, such as a low condensate of a tetraalkoxysilane, but from the viewpoint of excellent reactivity, it is preferable that the tetraalkoxysilane is 50 mass% or more and the material other than the tetraalkoxysilane is 50 mass% or less, and it is more preferable that the tetraalkoxysilane is 90 mass% or more and the material other than the tetraalkoxysilane is 10 mass% or less, out of 100 mass% of the total materials constituting the silica particles.
The solution (B) may contain no solvent but only tetraalkoxysilane, but preferably contains a solvent because of excellent dispersibility of tetraalkoxysilane in the reaction solution.
Examples of the solvent in the solution (B) include methanol, ethanol, propanol, isopropanol, and ethylene glycol. These solvents may be used singly or in combination of two or more. Among these solvents, the solvents used in the hydrolysis reaction and the condensation reaction are preferably alcohols, more preferably methanol and ethanol, and even more preferably methanol, because the solvents are the same as the by-product solvents and are excellent in production convenience.
The concentration of the tetraalkoxysilane in the solution (B) is preferably 60 to 95 mass%, more preferably 70 to 90 mass%, in 100 mass% of the solution (B). When the concentration of the tetraalkoxysilane in the solution (B) is 60 mass% or more, the reaction solution tends to be uniform. In addition, when the concentration of the tetraalkoxysilane in the solution (B) is 95 mass% or less, the formation of gel-like substance can be suppressed.
The concentration of the solvent in the solution (B) is preferably 5 to 40 mass%, more preferably 10 to 30 mass%, of 100 mass% of the solution (B). When the concentration of the solvent in the solution (B) is 5 mass% or more, the formation of gel-like substance can be suppressed. In addition, when the concentration of the solvent of the solution (B) is 40 mass% or less, the reaction solution becomes uniform easily.
The rate of addition of the solution (B) per hour relative to the volume of the solution (A) is preferably 0.02 kg/hr/L to 1.3 kg/hr/L, more preferably 0.05 kg/hr/L to 0.8 kg/hr/L. When the rate of addition of the solution (B) is 0.02 kg/hr/L or more, the productivity of the silica particles is excellent. In addition, when the rate of addition of the solution (B) is 1.3 kg/hr/L or less, the formation of gel-like substance can be suppressed.
Solution (C) is a solution comprising water, preferably further comprising a base catalyst.
Examples of the base catalyst that can be contained in the solution (C) include ethylenediamine, diethylenetriamine, triethylenetetramine, ammonia, urea, ethanolamine, and tetramethylammonium hydroxide. These base catalysts may be used singly or in combination of two or more. Among these base catalysts, ammonia is preferred because of its excellent catalytic activity, easy control of particle shape, suppression of mixing of metal impurities, high volatility, and excellent removability after hydrolysis and condensation reactions.
The solution (C) contains water as a solvent, and examples of the solvent other than water include methanol, ethanol, propanol, isopropanol, and ethylene glycol. The solvent other than water may be used alone or in combination of two or more. Among the solvents of the solution (C), only water or a combination of water and alcohol is preferable, and only water is more preferable, because the solvents used in the hydrolysis reaction and the condensation reaction are the same as the solvents as by-products, and the convenience in production is excellent.
The concentration of the base catalyst in the solution (C) is preferably 0 mass% to 10 mass% in 100 mass% of the solution (C). The alkali catalyst in the solution (C) may be 0 mass% or not, that is, may be contained, but in the case of containing the alkali catalyst, the concentration thereof is preferably 0.5 mass% or more, more preferably 1 mass% or more. When the concentration of the base catalyst in the solution (C) is 0.5 mass% or more, the concentration of the base catalyst in the reaction solution can be easily adjusted from the start of the reaction to the end of the reaction. In addition, from the viewpoint of reducing the variation in the concentration of the base catalyst in the reaction liquid, the concentration of the base catalyst in the solution (C) is preferably 10 mass% or less, more preferably 6 mass% or less.
The concentration of water in the solution (C) is preferably 90 mass% to 100 mass% of the solution (C) in 100 mass%. The concentration of water in the solution (C) may be 100% by mass, that is, the solution (C) may be composed of only water, but when other components are contained, the concentration of water is preferably 99.5% by mass or less, more preferably 99% by mass or less. From the viewpoint of reducing the variation in the concentration of the base catalyst in the reaction liquid, the concentration of water in the solution (C) is preferably 90 mass% or more, more preferably 94 mass% or more. When the concentration of water in the solution (C) is 99.5 mass% or less, the concentration of the base catalyst in the reaction solution can be easily adjusted from the start of the reaction to the end of the reaction.
The concentration of the solvent other than water in the solution (C) is preferably the concentration of water and the remainder of the base catalyst.
The addition of the solution (B) and the solution (C) is preferably carried out in the liquid of the solution (A). By adding the solution (B) and the solution (C) to the liquid of the solution (a), when an alkali catalyst having high volatility typified by ammonia is to be used, and when hydrolysis reaction and condensation reaction are to be performed at a high reaction temperature, the miscibility of each component in the reaction liquid is improved, abnormal reaction in a gas can be suppressed, and the particle shape can be easily controlled. The term "adding to the liquid" means adding to the liquid below the liquid level, and the solution (B) and the solution (C) can be added to the liquid of the solution (A) by setting the supply outlet of the solution (B) and the supply outlet of the solution (C) to be below the liquid level of the solution (A).
The timing of adding the solution (B) and the solution (C) to the solution (a) may be the same or may be different as alternating, but is preferably the same in that the reaction composition is less varied and the operation does not become complicated.
The pH in the step of subjecting the tetraalkoxysilane to hydrolysis reaction and condensation reaction is 8.0 to 14, preferably 8.2 to 13, more preferably 8.5 to 12. When the pH in the above step is 8.0 or more, the reaction rate of the hydrolysis reaction and the condensation reaction is excellent, and aggregation of silica particles can be suppressed. In addition, when the pH in the above step is 14 or less, the shape of the silica particles is easily controlled, and the smoothness of the silica particle surface is excellent.
The method for producing silica particles of the present invention preferably includes a step of performing hydrolysis and condensation of an alkoxysilane in 600 minutes or less, more preferably includes a step of performing hydrolysis and condensation of an alkoxysilane in 400 minutes or less, and even more preferably includes a step of performing hydrolysis and condensation of an alkoxysilane in 170 minutes or less. When the reaction time is 600 minutes or less, the growth rate of the silica particles is moderately slow, and thus the reaction of the bonding bonds of the adjacent silicon atoms and the direct bonding of the bonding bonds of the silicon atoms is suppressed. This can reduce the deformation of the siloxane network of the silica particles, and can adjust the average pore volume of the atomic scale micropores of the silica particles to an appropriate range, which is preferable. In addition, when the reaction time is 30 minutes or more, the particle growth is not excessively fast, and the controllability of the particle diameter and the particle shape is excellent.
The concentration of water in the reaction system of the hydrolysis reaction and the condensation reaction is preferably maintained at 3 to 90 mass%, more preferably 5 to 30 mass%, and even more preferably 6 to 25 mass% of the total 100 mass% of the reaction system. When the concentration of water in the reaction system is 3 mass% or more, the hydrolysis reaction rate of the tetraalkoxysilane can be easily controlled. In addition, when the concentration of water in the reaction system is 90 mass% or less, the reaction balance between the hydrolysis reaction and the condensation reaction is good, and the particle shape can be easily controlled.
The concentration of the base catalyst in the reaction system of the hydrolysis reaction and the condensation reaction is preferably maintained at 0.5 to 2.0 mass%, more preferably at 0.6 to 1.5 mass%, based on 100 mass% of the total amount in the reaction system. When the concentration of the base catalyst in the reaction system is 0.5 mass% or more, aggregation of silica particles is suppressed, and dispersion stability of silica particles in the dispersion liquid is excellent. When the concentration of the base catalyst in the reaction system is 2.0 mass% or less, the reaction does not proceed too rapidly, and the reaction controllability is excellent.
The method for producing silica particles preferably further comprises the following step (1) in order to remove unnecessary components and to add necessary components.
And (1) a step of concentrating the obtained dispersion of silica particles and adding a dispersion medium.
The concentration of the dispersion liquid of the silica particles in the step (1) and the addition of the dispersion medium may be performed first.
The method for concentrating the dispersion of silica particles is not particularly limited, and examples thereof include a heat concentration method and a membrane concentration method.
The dispersion of silica particles is concentrated by a heat concentration method, and the dispersion may be concentrated by heating under normal pressure or reduced pressure.
The dispersion of silica particles is concentrated by a membrane concentration method, and membrane separation by ultrafiltration is preferable. The main purpose of ultrafiltration is to remove unwanted components, such as intermediates. The molecular weight cut-off of the ultrafiltration membrane used herein is selected to be that which is removed by filtration of the intermediate product from the dispersion, depending on the intermediate product.
Examples of the material of the ultrafiltration membrane include polysulfone, polyacrylonitrile, sintered metal, ceramic, carbon, and the like. Examples of the form of the ultrafiltration membrane include a spiral type, a tubular type, and a hollow fiber type.
Examples of the dispersion medium to be added to the dispersion liquid of the silica particles include water, methanol, ethanol, propanol, isopropanol, and ethylene glycol. These dispersing media may be used singly or in combination of two or more. Among these dispersion media, water and alcohol are preferable, and water is more preferable, because of excellent affinity with silica particles.
In view of improving the condensation degree of silica particles, the method for producing silica particles preferably further comprises the following step (2).
And (2) a step of subjecting the silica particle dispersion obtained in the step (1) to a pressure-heating treatment.
The pressure of the pressure heating treatment is preferably 0.10MPa to 2.3MPa, more preferably 0.12MPa to 2.0MPa. When the pressure of the pressure-heat treatment is 0.10MPa or more, the degree of condensation of the silica particles can be increased. When the pressure of the pressure-heat treatment is 2.3MPa or less, silica particles can be produced without significantly changing the average primary particle diameter, the average secondary particle diameter, the cv value, and the association ratio, and the dispersion stability of the silica sol is excellent.
The silica particles may be dispersed in a liquid by heating the dispersion liquid to a temperature equal to or higher than the boiling point of the dispersion medium under pressure. When the aqueous dispersion of silica particles is heated to 100 ℃ or higher in a sealed state, the pressure is the saturated water vapor pressure at that temperature.
The temperature of the pressure heating treatment is preferably 100 ℃ to 220 ℃, more preferably 110 ℃ to 180 ℃. When the temperature of the pressure heating treatment is 100 ℃ or higher, the degree of condensation of the silica particles can be increased. When the temperature of the pressure heating treatment is 220 ℃ or lower, silica particles can be produced without significantly changing the average primary particle diameter, the average secondary particle diameter, the cv value, and the association ratio, and the dispersion stability of the silica sol is excellent.
The time of the pressure heating treatment is preferably 0.25 to 10 hours, more preferably 0.5 to 8 hours. When the time of the pressure-heat treatment is 0.25 hours or longer, the degree of condensation of the silica particles can be increased. When the time of the pressure-heat treatment is 10 hours or less, silica particles can be produced without significantly changing the average primary particle diameter, the average secondary particle diameter, the cv value, and the association ratio, and the dispersion stability of the silica sol is excellent.
The pressure-heat treatment is more preferably carried out in an aqueous dispersion, because the condensation degree of silica particles can be improved without greatly changing the average primary particle diameter, the average secondary particle diameter, the cv value, and the association ratio.
The pH of the aqueous dispersion when the pressure-heat treatment is carried out is preferably 6.0 to 8.0, more preferably 6.5 to 7.8. When the pH is 6.0 or more in the pressure-heat treatment in the aqueous dispersion, gelation of the silica sol can be suppressed. When the pH is 8.0 or less in the pressure-heat treatment in the aqueous dispersion, the degree of condensation of the silica particles can be increased without significantly changing the average primary particle diameter, the average secondary particle diameter, the cv value, and the association ratio.
(Silica sol)
The silica sol of the present invention comprises the silica particles of the present invention.
The silica sol may be produced by directly using the silica particle dispersion of the present invention, or by removing unnecessary components from the silica particle dispersion of the present invention and adding the necessary components.
The silica sol of the present invention preferably comprises silica particles and a dispersion medium.
Examples of the dispersion medium in the silica sol include water, methanol, ethanol, propanol, isopropanol, and ethylene glycol. The dispersion medium in the silica sol may be used alone or in combination of two or more. Among these dispersion media in silica sol, water and alcohol are preferable, and water is more preferable, because of excellent affinity with silica particles.
The content of silica particles in the silica sol is preferably 3 to 50% by mass, more preferably 4 to 40% by mass, and even more preferably 5 to 30% by mass, based on 100% by mass of the total silica sol. When the content of silica particles in the silica sol is 3 mass% or more, the polishing rate of the object to be polished represented by a silicon wafer is excellent. In addition, when the content of silica particles in the silica sol is 50 mass% or less, aggregation of silica particles in the silica sol or polishing composition can be suppressed, and the silica sol or polishing composition is excellent in storage stability.
The content of the dispersion medium in the silica sol is preferably 50 to 97% by mass, more preferably 60 to 96% by mass, and even more preferably 70 to 95% by mass, based on 100% by mass of the total silica sol. When the content of the dispersion medium in the silica sol is 50 mass% or more, aggregation of silica particles in the silica sol and the polishing composition can be suppressed, and the silica sol and the polishing composition are excellent in storage stability. Further, when the content of the dispersion medium in the silica sol is 97 mass% or less, the polishing rate of the object to be polished represented by a silicon wafer is excellent.
The content of silica particles and the dispersion medium in the silica sol can be set to a desired range by removing unnecessary components from the components in the obtained silica particle dispersion and adding the necessary components.
The silica sol may contain, in addition to the silica particles and the dispersion medium, other components such as an oxidizing agent, a preservative, a mold inhibitor, a pH adjuster, a pH buffer, a surfactant, a chelating agent, and an antimicrobial agent, as required, within a range not to impair the performance thereof.
In particular, from the viewpoint of excellent storage stability of the silica sol, it is preferable to include an antimicrobial agent in the silica sol.
Examples of the antimicrobial agent include hydrogen peroxide, ammonia, quaternary ammonium hydroxide, quaternary ammonium salt, ethylenediamine, glutaraldehyde, methylparaben, and sodium chlorite. These antimicrobial agents may be used singly or in combination of two or more. Among these antimicrobial agents, hydrogen peroxide is preferred because of its excellent affinity with silica sol.
Antibacterial antimicrobial agents also include substances commonly referred to as bactericides.
The content of the antimicrobial agent in the silica sol is preferably 0.0001 to 10 mass%, more preferably 0.001 to 1 mass%, based on 100 mass% of the total silica sol. When the content of the antimicrobial agent in the silica sol is 0.0001% by mass or more, the storage stability of the silica sol is excellent. When the content of the antimicrobial agent in the silica sol is 10 mass% or less, the original performance of the silica sol is not impaired.
The pH of the silica sol is preferably 6.0 to 8.0, more preferably 6.5 to 7.8. When the pH of the silica sol is 6.0 or more, dispersion stability is excellent, and aggregation of silica particles can be suppressed. Further, when the pH of the silica sol is 8.0 or less, dissolution of silica particles is prevented, and long-term storage stability is excellent.
The pH of the silica sol can be set to a desired range by adding a pH adjuster.
(Polishing composition)
The polishing composition of the invention comprises the silica sol of the invention.
The polishing composition of the present invention preferably contains a water-soluble polymer in addition to the silica sol of the present invention.
The water-soluble polymer improves the wettability of the polishing composition to a polishing object represented by a silicon wafer. The water-soluble polymer is preferably a polymer having a functional group with high water affinity, which has high affinity with the surface silanol groups of the silica particles, and the silica particles and the water-soluble polymer are more closely and stably dispersed in the polishing composition. Therefore, when polishing an object to be polished, typically a silicon wafer, the effects of the silica particles and the water-soluble polymer act synergistically.
Examples of the water-soluble polymer include cellulose derivatives, polyvinyl alcohol, polyvinylpyrrolidone, copolymers having a polyvinylpyrrolidone skeleton, and polymers having a polyoxyalkylene structure.
Examples of the cellulose derivative include hydroxyethyl cellulose, hydroxyethyl cellulose subjected to hydrolysis, hydroxypropyl cellulose, hydroxyethyl methylcellulose, hydroxypropyl methylcellulose, methyl cellulose, ethyl hydroxyethyl cellulose, and carboxymethyl cellulose.
Examples of the copolymer having a polyvinylpyrrolidone skeleton include a graft copolymer of polyvinyl alcohol and polyvinylpyrrolidone.
Examples of the polymer having a polyoxyalkylene structure include polyoxyethylene, polyoxypropylene, and a copolymer of ethylene oxide and propylene oxide.
These water-soluble polymers may be used singly or in combination of two or more. Among these water-soluble polymers, cellulose derivatives are preferable, and hydroxyethylcellulose is more preferable, because they have a high affinity with silanol groups on the surface of silica particles and act synergistically to impart good hydrophilicity to the surface of the object to be polished.
The mass average molecular weight of the water-soluble polymer is preferably 1000 to 3000000, more preferably 5000 to 2000000, and even more preferably 10000 to 1000000. When the water-soluble polymer has a mass average molecular weight of 1000 or more, the hydrophilicity of the polishing composition is improved. When the water-soluble polymer has a mass average molecular weight of 3000000 or less, the affinity with silica sol is excellent, and the polishing rate to the object to be polished represented by a silicon wafer is excellent.
The mass average molecular weight of the water-soluble polymer was measured by size exclusion chromatography under the condition that 0.1mol/L NaCl solution was used as a mobile phase in terms of polyethylene oxide.
The content of the water-soluble polymer in the polishing composition is preferably 0.02 to 10 mass%, more preferably 0.05 to 5 mass%, based on 100 mass% of the total amount of the polishing composition. When the content of the water-soluble polymer in the polishing composition is 0.02 mass% or more, the hydrophilicity of the polishing composition is improved. In addition, when the content of the water-soluble polymer in the polishing composition is 10 mass% or less, aggregation of silica particles at the time of preparation of the polishing composition can be suppressed.
The polishing composition of the present invention may contain, in addition to the silica sol and the water-soluble polymer, other components such as an alkaline compound, a polishing accelerator, a surfactant, a hydrophilic compound, a preservative, a mold inhibitor, a pH adjuster, a pH buffer, a surfactant, a chelating agent, and an antimicrobial agent, as required, within a range not to impair the performance thereof.
In particular, the polishing composition preferably contains an alkali compound, since chemical polishing (chemical etching) can be performed by applying a chemical action to the surface of the object to be polished typified by a silicon wafer, and the polishing rate of the object to be polished typified by a silicon wafer can be improved by the synergistic effect of silanol groups on the surface of silica particles.
Examples of the basic compound include organic basic compounds, alkali metal hydroxides, alkali metal hydrogencarbonates, alkali metal carbonates, and ammonia. These basic compounds may be used singly or in combination of two or more. Among these basic compounds, ammonia, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ammonium bicarbonate, and ammonium carbonate are preferable, ammonia, tetramethylammonium hydroxide, and tetraethylammonium hydroxide are more preferable, and ammonia is still more preferable, because of high water solubility and excellent affinity with silica particles and water-soluble polymers.
The content of the alkaline compound in the polishing composition is preferably 0.001 to 5% by mass, more preferably 0.01 to 3% by mass, based on 100% by mass of the total amount of the polishing composition. When the content of the alkaline compound in the polishing composition is 0.001 mass% or more, the polishing rate of the object to be polished represented by a silicon wafer can be increased. Further, when the content of the basic compound in the polishing composition is 5 mass% or less, the polishing composition is excellent in stability.
The pH of the polishing composition is preferably 8.0 to 12.0, more preferably 9.0 to 11.0. When the pH of the polishing composition is 8.0 or more, aggregation of silica particles in the polishing composition can be suppressed, and the dispersion stability of the polishing composition is excellent. In addition, when the pH of the polishing composition is 12.0 or less, dissolution of silica particles can be suppressed, and the stability of the polishing composition is excellent.
The pH of the polishing composition can be set to a desired range by adding a pH adjuster.
The polishing composition is obtained by mixing the silica sol of the present invention, a water-soluble polymer and other components added as needed, but may be prepared at a high concentration temporarily in view of storage and transportation, and may be diluted with water or the like immediately before polishing.
(Polishing method)
The polishing method of the present invention is a method of polishing using the polishing composition comprising the silica sol of the present invention.
The polishing composition is preferably used.
Specific polishing methods include, for example, a method in which the surface of a silicon wafer is pressed against a polishing pad, the polishing composition of the present invention is dropped onto the polishing pad, and the surface of the silicon wafer is polished.
(Method for manufacturing semiconductor wafer)
The method for producing a semiconductor wafer of the present invention is a method comprising a step of polishing using the polishing composition of the present invention, and specific polishing compositions and polishing methods are as described above.
Examples of the semiconductor wafer include a silicon wafer and a compound semiconductor wafer.
(Method for manufacturing semiconductor device)
The method for producing a semiconductor device of the present invention is a method comprising a step of polishing using the polishing composition of the present invention, and specific polishing compositions and polishing methods are as described above.
Examples of the polishing object include metals such as Si, cu, W, ti, cr, co, zr, hf, mo, ta, ru, au, pt, ag, al, ni, and metal compounds such as oxides, nitrides, and silicides, and intermetallic compounds of the metals. Among these polishing objects, metal and metal oxide may be preferably used, and metal oxide may be particularly preferably used.
(Use)
The silica particles of the present invention and the silica sol of the present invention can be preferably used for polishing, for example, polishing of semiconductor materials such as silicon wafers, polishing of electronic materials such as hard disk substrates, polishing in planarization step (chemical mechanical polishing) in the production of integrated circuits, polishing of synthetic quartz glass substrates used in photomasks or liquid crystals, polishing of magnetic disk substrates, and the like, and among these, polishing of silicon wafers and chemical mechanical polishing can be particularly preferably used.
As described above, the following matters are disclosed in the present specification.
<1>
A silica particle having an average pore volume of atomic-scale micropores measured by positron annihilation of 0.35nm 3 or more.
<2>
The silica particle according to <1>, wherein the average pore volume of the atomic scale micropores measured by positron annihilation is 0.40nm 3 or more.
<3>
The silica particle according to <1> or <2>, wherein the average pore volume of the atomic scale micropores measured by positron annihilation method is 1.0nm 3 or less.
<4>
The silica particles according to any one of <1> to <3>, wherein the average pore volume of the atomic scale micropores measured by positron annihilation is 0.80nm 3 or less.
<5>
The silica particle according to any one of <1> to <4>, wherein the average pore volume of the nano-scale pores measured by positron annihilation is 5.4nm 3 or less.
<6>
The silica particles according to any one of <1> to <5>, wherein the volume of pores having a diameter of 2nm or less as measured by a nitrogen adsorption method is 0.0070cm 3/g or less.
<7>
The silica particles according to any one of <1> to <6>, wherein the refractive index is 1.390 or more.
<8>
The silica particles according to any one of <1> to <7>, wherein the metal impurity content is 5ppm or less.
<9>
The silica particles according to any one of <1> to <8>, wherein the silica particles comprise a tetraalkoxysilane condensate as a main component.
<10>
A method for producing silica particles according to any one of <1> to <9>, comprising the step of carrying out hydrolysis reaction and condensation reaction of alkoxysilane in 600 minutes or less.
<11>
A silica sol comprising the silica particles according to any one of <1> to <9 >.
<12>
A polishing composition comprising the silica sol of <11 >.
<13>
A polishing method comprising polishing with the polishing composition of <12 >.
<14>
A method for producing a semiconductor wafer, comprising the step of polishing with the polishing composition of <12 >.
<15>
A method for manufacturing a semiconductor device, comprising the step of polishing with the polishing composition of <12 >.
Examples
The present invention will be described in further detail with reference to examples, but the present invention is not limited to the description of the examples below unless departing from the gist thereof.
(Measurement of average pore volume of nanoscale pores and average pore volume of atomic-level pores)
Using a positron beam life measuring apparatus (institute of industrial and technology), a positron life spectrum was obtained as follows. The silica particles obtained in examples and comparative examples were dispersed to obtain a dry powder of silica particles. The dried powder of silica particles was placed in a sample holder. The positron lifetime spectrum was obtained by irradiating the dried powder of silica particles with positrons at a vacuum level of 4×10 -4 Pa and a vacuum level of 20 ℃. The energy of the positron incident was set to 10keV.
The positron life spectrum obtained was fitted to the linear sum of four exponential functions to determine the positron average life of each component. Two of the four components having a short lifetime are components not derived from the sample, and one of the remaining two components having a short lifetime is a component derived from the atomic scale micropores, and the other is a component derived from the nano scale.
The positron average lifetime is converted to an average pore volume using the following equation.
(Atomic pore)
[ Number 5]
Wherein,
[ Number 6]
Τ is the average lifetime of positrons, R is the average radius of atomic scale pores, Δr is a correction value for the radius of atomic scale pores, and V is the average pore volume of atomic scale pores.
(Nanoscale pores)
[ Number 7]
Wherein,
[ Number 8]
Τ is the average lifetime of positrons, R is the average radius of the nano-sized pores, R 0 is the correction value of the radius of the nano-sized pores, λ T is the annihilation rate of normal electron-even in vacuum, and V is the average pore volume of the nano-sized pores.
(Measurement of refractive index)
The silica particles obtained in examples and comparative examples were dispersed to obtain a dry powder of silica particles. A10 mL glass bottle was charged with 0.1g of a dry powder of silica particles, the ratio of superfine 2-propanol to superfine toluene was changed, and the supernatant liquid obtained when the powder in the glass bottle became transparent was measured by an Abbe refractometer "RX-7000 alpha" (model name, ATAGO, co., ltd.) as the refractive index of the silica particles.
(Measurement of average Primary particle diameter)
The silica particle dispersions obtained in examples and comparative examples were dried at 150℃and the specific surface area of the silica particles was measured by an automatic specific surface area measuring device "BELSORP-MR1" (model name, microtrac-Bel Co., ltd.) and the average primary particle diameter was calculated by using the following formula (2) and setting the density to 2.2g/cm 3.
Average primary particle diameter (nm) =6000/(specific surface area (m 2/g) ×density (g/cm 3))..
(Measurement of average Secondary particle size)
The silica particle dispersions obtained in examples and comparative examples were subjected to measurement of the average secondary particle diameter of silica particles using a dynamic light scattering particle diameter measuring apparatus "Zetasizer Nano ZS" (model name, MALVERN PANALYTICAL).
(Measurement of volume of micropores having a diameter of 2nm or less by Nitrogen adsorption)
The silica particle dispersions obtained in examples and comparative examples were dried at 300℃and the adsorption isotherm of nitrogen gas to silica particles was measured by using a pore distribution measuring apparatus "Nova-touch" (model name, ANTON PAAR, inc.), and the volume of pores having a diameter of 2nm or less was determined by analysis by the BJH method.
(Mechanical Strength)
The silica particles obtained in examples and comparative examples were evaluated for mechanical strength suitable for polishing a substrate having a metal oxide film on the surface thereof according to the following criteria.
The mechanical strength was estimated to be extremely suitable for polishing.
The mechanical strength was estimated to be suitable for grinding.
The mechanical strength was estimated to be unsuitable for grinding.
(Storage stability)
The silica particles obtained in examples and comparative examples were evaluated for storage stability according to the following criteria.
It is estimated that the storage stability is extremely excellent.
And B, it is estimated that the storage stability is excellent.
And C, the storage stability is estimated to be poor.
Example 1
A solution (B) of tetramethoxysilane and methanol at a mass ratio of 5.7:1 and a solution (C) of 6.6 mass% aqueous ammonia solution were prepared, respectively. A reaction tank equipped with a thermometer, a stirrer, a supply pipe, and a distillation line is charged with a solution obtained by previously mixing methanol, pure water, and ammonia
(A) . The concentration of water in the solution (a) was set to 15 mass%, and the concentration of ammonia in the solution (a) was set to 2.4 mass%.
To 100 parts by volume of the solution (A) were added 63.6 parts by volume of the solution (B) and 24.6 parts by volume of the solution (C) at a constant rate over 153 minutes while maintaining the temperature of the reaction solution at 50 ℃. The obtained silica particle dispersion was subjected to removal of methanol and ammonia at an elevated temperature while adding pure water to adjust the liquid amount so that the silica particle content became about 20 mass%, thereby obtaining a silica particle dispersion having a silica particle content of about 20 mass%.
Example 2
The dispersion of silica particles obtained in example 1 was sealed in an autoclave, heated and maintained at 140 ℃ for 2 hours, thereby obtaining a dispersion of silica particles subjected to a pressurized heat treatment.
Comparative example 1
As a comparative example, silica particle dispersion "PL-3" manufactured by Hibiscus chemical industry Co.
The evaluation results of the silica particles of the above examples and comparative examples are shown in tables 1 and 2.
TABLE 1
TABLE 1
* The upper section is at the temperature of [ DEGC ], the lower section is at the time of [ h ]
TABLE 2
TABLE 2
Volume of pores having a diameter of 2nm or less measured by nitrogen adsorption method [ cm 3/g ]
Example 1 0.0041
Example 2 0.0018
As is clear from table 1, the silica particles obtained in example 1 have a larger average pore volume and a larger refractive index of atomic scale micropores, although the particle diameter is hardly changed from the silica particles obtained in comparative example 1. Since the average pore volume of the atomic-scale fine pores is within an appropriate range, it can be said that the deformation of the siloxane network of the silica particles obtained in example 1 is reduced. In the silica particles of example 2 obtained by subjecting the silica particles of example 1 to the heat treatment under pressure, the atomic scale micropores further become larger, and it can be said that the deformation of the siloxane network is further reduced. Thus, the mechanical strength and storage stability of the silica particles obtained in examples 1 to 2 were improved. In addition, in the step of polishing the object to be polished using the polishing composition containing the silica particles obtained in examples 1 to 2, the silica particles are less likely to be damaged.
As shown in table 2, the volume of the pores having a diameter of 2nm or less measured by the nitrogen adsorption method of the silica obtained in examples 1 to 2 was within a suitable range. Accordingly, it can be said that the fine pores which may become starting points of breakage are small in the silica, and thus the mechanical strength of the silica particles of examples 1 to 2 is improved.
Therefore, the silica sol and the polishing composition containing the silica particles of examples 1 to 2 can be used to efficiently polish the object to be polished without damaging the object to be polished, and the silica particles after polishing can be easily removed, thereby producing a high-quality polished article with good productivity.
While various embodiments have been described above, it is needless to say that the present invention is not limited to these examples. It is obvious to those skilled in the art that various modifications and corrections can be made within the scope of the appended claims, and it is needless to say that these modifications and corrections are also within the technical scope of the present invention. The components of the above embodiments may be arbitrarily combined within a range not departing from the gist of the invention.
The present application is based on japanese patent application No. 2022-099053 (japanese patent application No. 2022-099053), filed on 6/20 of 2022, the contents of which are incorporated herein by reference.
Industrial applicability
The silica particles of the invention and the silica sol of the invention can preferably be used for grinding applications. For example, the polishing composition can be used for polishing semiconductor materials such as silicon wafers, polishing electronic materials such as hard disk substrates, polishing (chemical mechanical polishing) in planarization steps in the manufacture of integrated circuits, polishing of synthetic quartz glass substrates used for photomasks and liquid crystals, polishing of magnetic disk substrates, and the like. Among them, chemical mechanical polishing for silicon wafers can be particularly preferred.

Claims (15)

1.一种二氧化硅粒子，其中，1. A silicon dioxide particle, wherein 通过正电子湮没法测定出的原子级细孔的平均孔容为0.35nm3以上。The average pore volume of atomic-scale pores measured by positron annihilation is 0.35 nm 3 or more. 2.根据权利要求1所述的二氧化硅粒子，其中，2. The silica particles according to claim 1, wherein 通过正电子湮没法测定出的原子级细孔的平均孔容为0.40nm3以上。The average pore volume of atomic-scale pores measured by positron annihilation is 0.40 nm 3 or more. 3.根据权利要求1所述的二氧化硅粒子，其中，3. The silica particles according to claim 1, wherein 通过正电子湮没法测定出的原子级细孔的平均孔容为1.0nm3以下。The average pore volume of atomic-scale pores measured by positron annihilation is 1.0 nm 3 or less. 4.根据权利要求1所述的二氧化硅粒子，其中，4. The silica particles according to claim 1, wherein 通过正电子湮没法测定出的原子级细孔的平均孔容为0.80nm3以下。The average pore volume of atomic-scale pores measured by positron annihilation is 0.80 nm 3 or less. 5.根据权利要求1所述的二氧化硅粒子，其中，5. The silica particles according to claim 1, wherein 通过正电子湮没法测定出的纳米级细孔的平均孔容为5.4nm3以下。The average pore volume of nanoscale pores measured by positron annihilation method is 5.4 nm 3 or less. 6.根据权利要求1所述的二氧化硅粒子，其中，6. The silica particles according to claim 1, wherein 通过氮气吸附法测定出的直径2nm以下的细孔的容积为0.0070cm3/g以下。The volume of pores having a diameter of 2 nm or less measured by a nitrogen adsorption method is 0.0070 cm 3 /g or less. 7.根据权利要求1所述的二氧化硅粒子，其中，7. The silica particles according to claim 1, wherein 折射率为1.390以上。The refractive index is 1.390 or more. 8.根据权利要求1所述的二氧化硅粒子，其中，8. The silica particles according to claim 1, wherein 金属杂质含有率为5ppm以下。The metal impurity content is less than 5 ppm. 9.根据权利要求1所述的二氧化硅粒子，其中，9. The silica particles according to claim 1, wherein 以四烷氧基硅烷缩合物为主要成分。The main component is tetraalkoxysilane condensate. 10.一种二氧化硅粒子的制造方法，其是权利要求1～9中任一项所述的二氧化硅粒子的制造方法，包括：10. A method for producing silicon dioxide particles, which is the method for producing silicon dioxide particles according to any one of claims 1 to 9, comprising: 在600分钟以下进行烷氧基硅烷的水解反应和缩合反应的工序。The step of the hydrolysis reaction and the condensation reaction of the alkoxysilane is performed for 600 minutes or less. 11.一种硅溶胶，其包含权利要求1～9中任一项所述的二氧化硅粒子。11 . A silica sol comprising the silica particles according to claim 1 . 12.一种研磨组合物，其包含权利要求11所述的硅溶胶。12 . An abrasive composition comprising the silica sol according to claim 11 . 13.一种研磨方法，其使用权利要求12所述的研磨组合物进行研磨。13. A grinding method, comprising grinding using the grinding composition according to claim 12. 14.一种半导体晶片的制造方法，其包括：14. A method for manufacturing a semiconductor wafer, comprising: 使用权利要求12所述的研磨组合物进行研磨的工序。A step of polishing using the polishing composition according to claim 12. 15.一种半导体器件的制造方法，其包括：15. A method for manufacturing a semiconductor device, comprising: 使用权利要求12所述的研磨组合物进行研磨的工序。A step of polishing using the polishing composition according to claim 12.
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